Ender 3 Pro Z-Axis troubleshooting

New to the forum because I’m doing some troubleshooting for my son. I haven’t been able to find this issue described elsewhere. Sorry for the long post, just trying to be thorough.

He’s had an Ender 3 Pro for just over a year now - Marlin bugfix-2.0.x, 2021-12-07. BTT SKR Mini E3 V3.0 board - and we’re running into issues with Z axis positioning. Something is preventing the Z home from being set at it’s actual zero position.

The couple ways we’ve experienced this issue:

-Before we start any print, we have to manually position the Z axis at the bed by disabling the stepper motors. But upon starting the print, the Z-axis raises up off the bed, runs what I’ve assumed is an extruder purge along the Y-axis, moves over to the print location, but then does not drop back down to the bed. If the print is paused, the extruder is moved to a rest position (X = 0, Y = max, Z = same height) and there is not an option to disable the stepper motors so we can drop the nozzle back to the bed. The only option for adjusting the Z-axis is in the positive direction. With the factory motherboard, this same issue would occur, but the print could be paused, the nozzle would stay in the same position, and we could disable the steppers and drop the Z back down to the bed.

-When just trying to configure - not printing - I can disable the stepper motors and bring the Z down to its lowest position (right at the limit switch) and try to ‘Set Home Offsets’, I get a message that says ‘Home XYZ First’. But when I Auto Home, the Z raises up approximately 6mm. If I go to adjust the Z axis using the screen and controls, I can only adjust in the positive direction, raising it up higher.

The really weird part is that if I ‘Auto Home’ again, the X and Y both return to zero but the Z raises up another 6mm and I cannot lower it using the controls. I can only lower it by disabling the steppers, but then the described cycle starts over again.

The Z-limit switch seems to be positioned well, no Z-probe currently installed. My assumption is this is a code issue that needs to be resolved, but it’s beyond my basic understanding of that. I recently installed what I thought was the most recent firmware for the board, but I’m probably missing something there as well.

Any insights are greatly appreciated, especially considering the machine can’t currently print and my 11 year old is pretty frustrated about what is currently a fancy paperweight.

Hi and welcome to the forums!

I have only ever come across one other person who has had this issue before and it turned out to be that they had over tightened the bed screws on all 4 corners which was causing the bed to be too low for the nozzle to reach it.

To rectify the problem it was a case of loosening off all of the screws to bring the bed up higher and then proceed to work around each corner re-leveling the bed to the correct height.

If you need the guide for the bed leveling you should be able to find it on page 7 of the User Manual available here:
Ender 3 Pro - Downloads and User Manual

Hope that helps and good luck, hope your 11 year old gets back to printing soon!

Thanks - unfortunately I don’t think that its a matter of the bed being too low. In the past using the original motherboard, we were always able to pause the print, disable the stepper motors, and manually drop the Z down to the bed. New motherboard doesn’t have the capacity to do that.

I did run another test today and I was able to complete a print after baby stepping the Z…the only issue was it took me more than 3 minutes to dial through thousandths of mm’s to get to the -14.655mm position needed to be at the bed. By that point I had missed the first couple layers.

-14.655mm = original unexplained starting point of ~6mm + another vertical advancement of ~6mm + the couple layers that were missed while dropping the nozzle.

I have a few other tests to run in the next few days and we will be installing a Z-probe - seems to be enough overlap in tweaking and troubleshooting that may as well do them both at the same time.

I would definitely recommend checking a few things over such as the screws, the z limit and also the hot end itself to make sure nothing has either come loose or been knocked out of place/alignment.

You should definitely not be having to pause a print and manually lower the z axis to get the printer to print. 3D printers are designed to know where the z limit is either via manual bed leveling combined with a z limit switch, or, via a bed probe. Once that is configured there should be no need for the user to intervene once the print is initiated.

I would definitely recommend delving deeper and checking everything over to ensure nothing is out of place as I have never heard of anyone having to manually intervene when starting a print to lower the nozzle closer to the bed apart from during initial setup/calibration of the z offset.

If all else fails I would recommend putting the old original board back in and testing with that if you can as that would help rule out any issues being caused by the new board.

Good luck and let us know if you come up with a solution as would love to know.

Promising development…

While testing more, I noticed that the first motion on homing was always up. Z would never drop, which got me thinking about hardware and perhaps no signal from the Z stop. Sure enough, Z stop wasn’t plugged in. Must be some default in the programming to lift first.

Still need to do more testing, but pretty hopeful that this is the fix. Just wanted to share in case others run in to the same problem.

Glad to hear you have made some progress with diagnosing the issue, here is hoping you can enjoy 3D printing again :slight_smile:

Thanks for reporting back your progress, like you say always handy reference for others who may have similar issues.